It's a third party - they'd have to pay license fees.
Plus, I doubt skype is reliable enough for in-game chat.
Wow - so skype's proprietary voIP codec rivals most of the G.711 and G.729 SIP codecs carriers use.
Most Tier 1 carriers such as British Telecom, AT&T, Global Crossing, etc use SBC and gateways that one day dream of being as impressive as skypes proprietary VoIP codec.
Skype would make the client for PS3 to service their paying users. For some reason they have Skype for PSP but not PS3...
XBL's VoIP codecs are a shitstain on a prison wall compared to Skype.
Safe Harbor was brill for buying Skype - they very well could become the global dominating carrier for VoIP/TDM call origination and termination services by 2015.